Hey, did you know that the Aztecs made good old guac in the 16th century? And now you are smarter. Damn it, you can't come here to learn anything.
Anywho, I read at Lifehacker about pouring water on top of guacamole and it wouldn't turn brown. I have tried pushing a lettuce leaf on guacamole and putting the pit back in the bowl with the guac and nothing worked. My green goodness was always brown after a few hours. But this worked and worked well! Just pour about half an inch of water on top of it and put a lid on it. When you want to eat it, just pour it off and stir. Works like a charm!!!!!